The invention relates to the cooling of a circuit element, and, more particularly, the invention relates to an apparatus for dissipating heat from a circuit element mounted on a printed circuit board.
In general, heatsinks dissipate heat away from integrated circuits (ICs) to the surrounding air. Presently, there are two main approaches to installing such heatsinks. In the first approach, the heatsink is bonded to the top of the IC. In bonding, the bond line between the IC and the heatsink must be sufficiently thin to ensure minimal thermal resistance through the bonding material.
Unfortunately, delamination of the heatsink can result if the IC generates too much heat. The loose heatsink could come in contact with other circuitry and cause an electrical short, and the now improperly bonded heatsink will not dissipate heat from the IC. Bonding is thus a poor solution when maximal heat dissipation is required.
In the second approach, the heatsink is mechanically mounted to the printed circuit board (PCB) such that the IC is sandwiched between the heatsink and the PCB. Specifically, the heatsink is mounted by either securing the heatsink to the IC via clips that attach to the underside of the IC package (i.e., piggyback mounting), or mounting the heatsink to the PCB using spring clips or screws. Piggyback mounts are typically not used with ICs having a low profile package, such as a quad flat pack (QFP) or a ball grid array (BGA) package, because there is minimal gap between the IC and the PCB for attaching the heatsink. Attaching the heatsink to the PCB using spring clips or screws requires isolating the mounting area from the traces of the PCB thereby reducing the available space for circuit routing. As such, knowledge of heatsink placement is required before design and sometimes results in enlargement of the PCB to accommodate the heatsink.
Therefore, a need exists in the art for a heatsink arrangement that provides maximum heat dissipation without being bonded to the IC or being mounted to the PCB or the under edge of the IC package.
The disadvantages associated with the prior art are overcome by an apparatus for dissipating heat from a circuit element mounted to a PCB. In an embodiment of the invention, a heatsink for dissipating heat from an (Integrated Circuit) IC mounted to the PCB is coupled to a surrounding structure of the PCB. The surrounding structure is a RF shield. The heatsink comprises a connector for thermal contact with an IC, and a pair of arms for dissipating heat and for coupling the heatsink to the surrounding structure without contacting the PCB. If the ICs have electrically conductive packages, non-electrically conductive thermal spacers are inserted between the connector and the corresponding IC to electrically isolate the heatsink from the IC. Additionally, each arm has a tip extending perpendicularly therefrom, substantially increasing the surface area thereof for increased heat dissipation and for structural stability.
The heatsink is mounted to the surrounding structure using bumps attached to the tips of each arm. Holes in the surrounding structure accept the bumps attached to the tips of each arm. In alternative embodiments of the invention, the heatsink is coupled to slots or holes in the surrounding structure via rivets, pin plugs, pegs or screws on the tips of the arms of the heatsink. Because the heatsink does not come into contact with the PCB, the PCB can be made smaller and trace routing is maximized.
Further embodiments of the present invention will become apparent from the detailed description contained hereinafter. It should be understood, however, that the detailed description and specific examples are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.